Reliability of Measurement and Power of Significance Tests Based on Differences

Applied Psychological Measurement - Tập 17 Số 1 - Trang 1-9 - 1993
Donald W. Zimmerman1, Richard H. Williams2, Bruno D. Zumbo3
1Carleton University
2University of Miami
3University of Ottawa

Tóm tắt

The power of significance tests based on differ ence scores is indirectly influenced by the reliability of the measures from which differences are obtained. Reliability depends on the relative magnitude of true score and error score variance, but statistical power is a function of the absolute magnitude of these components. Explicit power calculations reaffirm the paradox put forward by Overall & Woodward (1975, 1976)—that significance tests of differences can be powerful even if the reliability of the difference scores is 0. This anomaly arises because power is a function of observed score variance but is not a function of reliability unless either true score variance or error score variance is constant. Provided that sample size, significance level, directionality, and the alternative hypothesis associated with a significance test remain the same, power always increases when population variance decreases, independently of reliability.

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Applied Psychological Measurement

Tập 17 Số 1

1-9

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